Sewing thread



3,308,616 Patented Mar. 14, 1 967 3,308,616 SEWING THREAD Kenneth RogerWilliams, Landenherg, Pa., assignor to E. I. du Pont de Nemonrs andCompany, Wilmington, Del, a corporation of Delaware No Drawing. FiledMar. 8, 1965, Ser. No. 438,073 9 Claims. (Cl. 57-153) This inventionrelates to an improved sewing thread and to a process for itsmanufacture.

The object of the present invention is to provide an improved sewingthread of synthetic, polymeric composition that will performsatisfactorily at high sewing speeds.

This and other objects will become apparent in the course of thefollowing specification and claims.

In accordance with the present invention, a novel sewing thread isprovided, twisted from novel continuous filament yarn formed from asynthetic linear polymer, e.g. from polyacrylonitrile, a polyamide, apolyester or a polyolefin, and said yarn uniformly bearing on itssurface from about 0.9% to about 11% by weight based on the weight ofthe said filament of a finish selected from the class consisting of (1)a mixture of from about by weight aluminum tristearate and 90% by weightdimethyl polysiloxane, (2) methyl-phenyl polysiloxane of about 18,000cs. viscosity and (3) a mixture of about 40% by weight methyl hydrogensiloxane and 60% by weight dimethyl siloxane, the finish having beenheat treated after the yarn bearing the finish has been twisted intothread. By being heat treated is meant that the finish is either meltedupon the yarn, polymerized thereon as a result of a thermally initiatedpolymerization or simply subjected to the heating experienced in theusual heat setting of the twist. This thread is preferably of a denierless than about 1500 and has a twist multipler within the range of fromabout 2.4 to about 4.3 wit-h a coefiicient of kinetic friction at 600 F.within the range of from 0.1 to about 0.35. The filament yarn from whichthe thread is twisted preferably has a denier of from about 4 to aboutdenier per filament, particularly from about 7 to about 16 denier perfilament. The filaments are characterized by a flexural rigidity withinthe range of 2.7 10 and 14.0 10 gram (centimeter)? The novel yarns forthis invention have a coefiicient of kinetic friction at 550 F.(measured prior to heat-treatment) within the range of from 0.10-0.38.

Finishes for this invention are those that permit the yarn filaments toretain their spatial integrity. Therefore, the filaments do not coalesceor become bonded to gether. It should 'be noted that the finish for thisinvention adheres to the filament preferably by a phase change, i.e., byeither melting and then resolidifying, or by in situ polymerization.While many finishes are oper able for this invention, the preferablefinishes are either aluminum tristearate in dimethyl polysiloxane or'themixture of methyl hydrogen siloxane and dimethyl siloxane;

The coefiicient of kinetic friction for the sewing thread is determinedto be the ratio of output-tension to input tension when the threadpasses at 260 yards per minute over 170 of the surface of a smoothchrome cylindrical /s-inch diameter pin. The pin surface is electricallyheated, and the temperature is adjustable from room temperature to morethan 600 F. In determining coefiicient of kinetic friction for yarn(according to the above-specified method) the yarn is first twisted togive approximately the same twist multiplier found in synthetic sewingthread.

The fiexural rigidity for the filament is determined by the loop methodaccording to P. W. Carlene (Journal of the Textile InstituteTransactions T-l59, 1950). A single filament is formed into a 1.5-1.6centimeter diameter continuous loop. The loop is flattened and thenelongated (extended) for 2 millimeters at a rate of 0.64 centimeter perminute. The force in milligrams to so elongate the loop is multiplied by2.72 10- to give the flexural rigidity in gram (centimeter)? Thisflexural rigidity is a function of filament denier, filamentcomposition, and moment of inertia of the filament cross-section. Thisfiexural rigidity is directly proportional to denier and vto the momentof inertia. That is, as denier and moment increases, flexural rigidityincreases. Of the polymers included within this invention, polyestersgenerally have the higher fiexural rigidity.

The following examples serve to illustrate this invention, and are notintended to limit it in any manner.

Example I A three-ply sewing thread, denier per ply, and twisted 228 x172 for a twist'multiplier of about 4.3 is constructed of continuous,hexalobal, 16 denier per filament, filaments spun from a melt ofpolyhexamethylene adipamide. A finish, consisting of a 40% dispersion inwater of the liquid mixture of about 60% liquid dimethyl siloxane and40% liquid methyl hydrogen siloxane (commercially available under thetrademark De Cetex 104 from the Dow Corning 'Corp. of Midland, Michigan)is applied to the yarn before twisting by passing the drawn yarn overthe cylindrical surface of a metering roll which roll is rotatablysustained, partly submerged, in a bath of the dispersion. The yarn,hearing about 8.7% by weight finish is packaged to be twisted intothread. The fiexural rigidity of the filaments of the untwisted yarn is8.6 10- gram (centimeter) and the coefficient of kinetic friction at 550F. is about 0.19 (measured prior to the heat-treatment specified below).

After twisting the yarn to form a 240-denier thread, the twist is set,and polymerization of the siloxanes is accomplished, by placing apackage of the thread in an oven at F. for about 3 hours. This thread isthen packaged. The finish, now a solid (substantially waterfree),polymerized material, is retained on the thread after a normal boil-offscour. The coetficient of friction of the final thread at 600 F. is0.27.

The sewing thread of the present invention, prepared as described above,is used on a Singer 600 Wl singleneedle, lock-stitch, sewing machineoperating at 4500 stitches per minute and 12 stitches per inch to sewthree layers of 9.4 ounces per square yard, 319 grams per square meter,56 x 40 cotton duck. This sewing is with satisfactory results for beyonda five minute test interval. The thread remains intact, the stitching isuniform, and the layers are firmly sewn together.

When the same thread is used to sew 3 layers of 9.4 oz./yd. cotton duckon 2. Singer 600 W-21 machine operating at 4000 stitches per minute, thefirst break occurs after 4.35 minutes of sewing. In a comparativecontrol A, wherein the yarn employed in the same sewing operation isidentical except that the finish is applied to the thread (instead ofbeing applied to the yarn before twisting), a break occurs in 1.48minutes. The coefficient of kinetic friction. at 600 F. for thiscomparative control is 0.38.

Two other comparative controls, B and C are pre-. pared. Each is formedfrom round filament and each t'hread'is of'3 ply construction. Yarncharacteristics are listed in Table I.

TABLE I Denier No.Fil. Denier Per Fil.

Flex. Rigidity 1 Geoff. Kin. Fric. 2

1 Gram (centimeter) 2 550 F.

3 Each yarn is coated with De Cetex 104 as taught above and twisted intothread. The twist multiplier, thread properties (including the threadcoeificient of kinetic friction) and minutes to breaking when sewingcomparative textiles at 4500 stitches per minute on a Singer 600 W1machine are listed in Table II.

TABLE II Twist Thread Coetficient Minutes Control Multiplier Denier ofKinetic To Break Friction 1 Example II Aluminum tristearate, applied asa dispersion of solid aluminum tristearate (MP. 180 C.) in silicone oil(dimethyl polysiloxane) is substituted for the De Cetex 104 of ExampleI. Twist setting is done at 140 F. for three hours followed by heatingat 248 F. for three hours to melt the finish on the thread. The yarnbears 5.0% by weight of the finish based on the weight of the yarn. Thealuminum tristearate finish is observed to be a solid on the filamentsof the twist-set thread, and the finish is retained on this thread afternormal boil-off scour. The coefiicient of kinetic friction of the yarn,containing aluminum tristearate, is about 0.18 at 550 F. while thethread has a coeflicient of kinetic friction at 600 F. of 0.27. Insewing (a Singer W1 machine at 4500 stitches/min.) this thread breaksafter 3.34 minutes of sewing.

Example 111 A De Cetex 104 finish is applied to a three-ply thread, 70denier per ply, twisted 228 x 17Z for a twist multiplier of 3.7 and ofround, S-denier filaments spun from a melt of polyethylene terephthalatein the same manner and in the same concentration as taught in Example Iexcept that twist setting is done at 185 F. The flexural rigidity of thefilaments is 2.77 10- gram (centimeter) and the coeflicient of kineticfriction of the thread is 0.27 at 600 F. The yarn bears 3.99% by weightof the finish, based on the Weight of the yarn. Thread breakage occursafter 4.17 minutes of sewing (Singer W1 at 4500 stitches/min).

Example IV A polyester, three-ply test sewing thread, 70 denier per ply,and twisted 22S x 172 for a twist multiplier of 3.7 is constructed ofyarn comprising hexalobal filaments, 10 denier per filament, spun from amelt of polyethylene terephthalate. The finish of Example I is appliedby the technique of this invention as taught in Example I. Aftertwisting, the thread is heat set at 185 F. The flexural rigidity of thefilaments is 10.9 10- gram (centimeter) the coefficient of kineticfriction of the yarn at 550 F. is 0.23, and the coefficient of kineticfriction of the thread at 600 F. is 0.26.

Sewability is determined using a Singer 600 W-1 machine, with a No. 12needle, operated at 4500 stitches per minute and 12 stitches per inch tosew 4 layers of 9.4 ounces per square yard 56 x 40 cotton duck followedby a Singer 281-1 machine with a No. 12 needle, operated at 5600stitches per minute and 12 stitches per inch to sew 3 layers of 9.4ounces per square yard 56 x 40 cotton duck. The median time for threadrupture for these two types of sewing is then determined. For the threadof this example it is observed to be 0.71 minute. When a control threadD is provided identical to the test thread of this example except thatthe finish does not contain methyl hydrogen siloxane (coefiicient offriction of the yarn being 0.37 at 550 F. and of the thread 0.84 at 600F.), thread rupture occurs after only 0.04 minute of this test. Controlthreads E and F are commercial #23/ nylon thread (230 denier), andcommercial #23 polyester thread (each being about 2 denier per filament,and twisted of 3 plies, 70 denier per ply), each bearing about 4% ofconventional finish. The nylon (E control) thread (with a coefficient offriction of 0.73 at 600 F.) ruptures after 0.09 minute, and thepolyester (F control) thread (with a coefficient of friction of 0.88 at600 F.) ruptures after 0.07 minute.

Example V About 2% by weight based on the weight of the yarn of liquidmethyl-phenyl polysiloxane (18,000 cs. viscosity), is applied followingthe technique of Example IV as a 10% solution of liquid methyl-phenyl.polysiloxane in carbon tetrachloride to the test yarn used in ExampleIV. The flexural rigidity of the filaments is about ]O.9 l0- gram(centimeter) and the coefiicient of kinetic friction of the thread at600 F. is 0.35. This thread is used on a Singer 600 W-l single-needle,lockstitch sewing machine operating at 4500 stitches per minute and 12stitches per inch, with a No. 12 Singer needle to sew 4 layers of 9.4ounces per square yard, 56 x 40 cotton duck with satisfactory resultsfor over 5 minutes. The thread remains intact, the stitching is uniform,and the layers are firmly sewn together.

The polymer composition of the filaments for this invention arepolyamides, polyesters, polyolefins and polyacrylonitrile.

Typical of preferred polyamides are poly(hexamethylene adipamide),poly(methaxylylene adipamide), and polyamides derived from paraxylenea,a-diamine and azelaic acid, and from 4,4-methylene biscyclohexylamideand aliphatic acids such as azelaic, sebacic, and dodecanedioic acids,and their homologs, and copolymers or melt-blends of the above-mentionedpolyamides, as well as copolymers with poly(hexamethyleneterephthalamide) and with poly(hexamethylene bibenzoamide).

Typical of preferred polyesters are poly(ethylene terephthalate),poly(hexa-hydro p xylylene terephthalate), poly(diphenylol propaneisophthalate) poly(bicyclohexyl dimethane bibenzoa-te), and polyestersfrom naphthalene dicarborylic acids.

Polypropylene is preferred among the polyolefins.

It is apparent that many variations and modifications of this inventionmay be accomplished without departmg from the spirit and scope of thepresent invention which is accordingly intended to be limited only bythe scope of the appended claims.

What is claimed is:

1. A sewing thread twisted from a continuous filament yarn formed from alinear, synthetic polymer and uni formly bearing on the surface of thesaid yarn from about 0.9% to about 11% by weight based on the weight ofthe said yarn of a heat-treated finish selected from the classconsisting of (1) a mixture of about 10% by weight aluminum tristearateand by weight dimethyl polysiloxane, (2) methyl phenyl polysiloxane ofabout 18,000 cs. viscosity and (3) a mixture of methyl hydrogen siloxaneand dimethyl siloxane, the filaments of the said yarn having a flexuralrigidity of from about 2.7 10 to x10 gram (centimeter) the finish havingbeen applied to the yarn before twisting and having been heat-treatedafter the yarn bearing the finish has been twisted.

2. The thread of claim 1 wherein item (3) is about 40% by weight methylhydrogen siloxane and about 60% by weight dimethyl siloxane.

3. The thread of claim 2 wherein the said polymer is a polyamide.

4. The thread of claim 2 wherein the said polymer is a polyester.

5. The thread of claim 2 wherein the said polymer is a polyolefin.

6. A multifilament continuous yam suitable for twisting into threadformed from a linear, synthetic polymer, the filaments of the said yarnhaving a flexural rigidity of from about 2.7)(10- to 14.0 10- gram(centimeter) and the said yarn having substantially uniformlydistributed over its surface from about 0.9% to about 11% by weight,based on the weight of the said yarn, of a finish selected from theclass consisting of (1) a mixture of about 10% by weight aluminumtristearate and 90% by weight dimethyl polysiloxane, (2) methyl-phenylpolysiloxane of 18,000 cs. viscosity and (3) a mixture of about 40% byweight methyl hydrogen siloxane and 60% by weight dimethyl siloxane.

7. The yarn of claim 6 wherein the said polymer is a polyarnide.

8. The yarn of claim 6 wherein the said polymer is a polyester.

9. The yarn of claim 6 wherein the said polymer is a polyolefin.

References Cited by the Examiner UNITED STATES PATENTS 2,392,805 1/1946Biefeld 57153 2,799,598 7/1957 Biefeld et a1 57140 X 2,959,910 11/1960Woodson 57153 3,081,193 3/1963 Stasse 117138.8 X 10 3,159,600 12/1964Watkins 117138.8 X

FRANK J. COHEN, Primary Examiner. J. PETRAKES, Assistant Examiner.

1. A SEWING THREAD TWISTED FROM A CONTINUOUS FILAMENT YARN FORMED FROM ALINEAR, SYNTHETIC POLYMER AND UNIFORMLY BEARING ON THE SURFACE OF THESAID YARN FROM ABOUT 0.9% TO ABOUT 11% BY WEIGHT BASED ON THE WEIGHT OFTHE SAID YARN OF A HEAT-TREATED FINISH SELECTED FROM THE CLASSCONSISTING OF (1) A MIXTURE OF ABOUT 10% BY WEIGHT ALUMINUM TRISTEARATEAND 90% BY WEIGHT DIMETHYL POLYSILOXANE, (2) METHYL PHENYL POLYSILOXANEOF ABOUT 18,000 CS. VISCOSITY AND (3) A MIXTURE OF METHYL HYDROGENSILOXANE AND DIMETHYL SILOXANE, THE FILAMENTS OF THE SAID YARN HAVING AFLEXURAL RIGIDITY OF FROM ABOUT 2.7X10**-4 TO 14.0X10**-4 GRAM(CENTIMETER)2 THE FINISH HAVING BEEN APPLIED TO THE YARN BEFORE TWISTINGAND HAVING BEEN HEAT-TREATED AFTER THE YARN BEARING THE FINISH HAS BEENTWISTED.